This invention relates to plastics packaged glass optical fibres. Glass optical fibres, typically those made of fused silica, are normally provided with a plastics protective coating immediately after they are drawn from preform. A primary function of such a coating is to preserve, so far as is practically possible, the initial strength of the freshly drawn fibre by protecting its surface from chemical attack and from mechanical damage resulting from it being allowed to contact any solid surface other than that of the coating itself. Typically the application of the initial plastics protective coating is followed by the application of one or more further coatings of plastics material to produce a complete plastics packaged optical fibre. Not all of these further coatings are necessarily applied on-line with the drawing of fibre from preform. The thicknesses, moduli and expansion coefficients of the individual layers comprising the complete plastics packaging are normally chosen to provide mechanical buffering from the fibre and protection against micro-bending. A typical three-layer structure comprises an acrylate inner layer, a nylon outer layer and, between two layers, an intermediate layer of lower modulus material. Although described as a three-layer package, the acrylate layer may be a composite layer built up from two or more component sub-layers applied in succession, those sub-layers being slightly different acrylate composition, and hence of slightly different modulus.